ZJIT: Fix Rust warnings (ruby#13813)

Author: st0012

zjit/src/hir.rs

@@ -3147,7 +3147,7 @@ mod validation_tests {
     fn one_block_no_terminator() {
         let mut function = Function::new(std::ptr::null());
         let entry = function.entry_block;
-        let val = function.push_insn(entry, Insn::Const { val: Const::Value(Qnil) });
+        function.push_insn(entry, Insn::Const { val: Const::Value(Qnil) });
         assert_matches_err(function.validate(), ValidationError::BlockHasNoTerminator(format!("{:?}", function), entry));
     }
 
@@ -3166,7 +3166,6 @@ mod validation_tests {
         let mut function = Function::new(std::ptr::null());
         let entry = function.entry_block;
         let side = function.new_block();
-        let exit = function.new_block();
         let val = function.push_insn(entry, Insn::Const { val: Const::Value(Qnil) });
         function.push_insn(entry, Insn::IfTrue { val, target: BranchEdge { target: side, args: vec![val, val, val] } });
         assert_matches_err(function.validate(), ValidationError::MismatchedBlockArity(format!("{:?}", function), entry, 0, 3));
@@ -3177,7 +3176,6 @@ mod validation_tests {
         let mut function = Function::new(std::ptr::null());
         let entry = function.entry_block;
         let side = function.new_block();
-        let exit = function.new_block();
         let val = function.push_insn(entry, Insn::Const { val: Const::Value(Qnil) });
         function.push_insn(entry, Insn::IfFalse { val, target: BranchEdge { target: side, args: vec![val, val, val] } });
         assert_matches_err(function.validate(), ValidationError::MismatchedBlockArity(format!("{:?}", function), entry, 0, 3));
@@ -3188,7 +3186,6 @@ mod validation_tests {
         let mut function = Function::new(std::ptr::null());
         let entry = function.entry_block;
         let side = function.new_block();
-        let exit = function.new_block();
         let val = function.push_insn(entry, Insn::Const { val: Const::Value(Qnil) });
         function.push_insn(entry, Insn::Jump ( BranchEdge { target: side, args: vec![val, val, val] } ));
         assert_matches_err(function.validate(), ValidationError::MismatchedBlockArity(format!("{:?}", function), entry, 0, 3));